During borehole-forming and completion operations, it is necessary to make up and/or break down long strings of tubular goods such as drill pipe and casing. The string of pipe may be thousands of feet long, and it is therefore necessary to transport pipe joints (approximately 33 to 45 feet in length) from a pipe rack located away from the rig up to the rig floor. When being tripped out of the hole, the string of pipe is broken down into separate joints and returned to the pipe rack.
The handling of oil well pipe is one of the most dangerous jobs on a drilling rig. Some of the pipe joints weigh thousands of pounds, and it is difficult to move the pipe from a horizontal position below and away from the rig into a vertical position overlying hole center in the rig.